42 THE HUMAN BODY. 



The socket on the outer end of the shoulder-blade, with 

 which the humerus forms the shoulder-joint, is very shal- 

 low, and allows of much freer movement than is permitted 

 by the deeper socket of the pelvis, into which the top of 

 the thigh bone fits. 



If we hold one humerus tightly and do not allow it to 

 rotate, we can still move the forearm bones so as to turn 

 the palm of the hand up or down ; no such movement is 

 possible between tibia and fibula. 



Cl C ? XT SfH 



FIG. 19. The bones of the foot. Ca, calcaneum, or heel bone; Ta, articular 

 Btuface for tibia on the astragalus ; Cb, the cuboid bone. 



In the foot the bones are much less movable than in 

 the hand, and are so arranged as to make a springy arch 

 (Fig. 19) which bears behind on the heel bone, Ca, and in 

 front on the far ends, Os, of the metatarsal bones ; over 

 the crown of the arch at Ta is the surface with which the 

 leg-bones articulate, and on which the weight of the body 

 bears when we stand. 



Which is deeper, the socket on shoulder-blade for humerus, or on 

 pelvic girdle for femur? 



Can the foot be turned round so as to bring its sole upwards? 

 Can the hand so as to bring the palm up? 



Are the hand or the foot bones more movable? How are the foot 

 bones arrans^d? On what points does the arch of the foot bear? On 

 what part of the arch is the weight of the body borne? 



